Coating compositions

Abstract

The present invention relates to an aqueous composition comprising at least one partially fluorinated copolymer in the form of particle powder, to a method for its preparation and to its use as a coating.

The invention claimed is: 
     
       1. A composition comprising an aqueous solvent and a solid portion, wherein:
 a) from 15 to 30% in weight/total weight of the solid portion consists of a first powder of at least one copolymer (F) in the form of particles having average size (D50) from 3 to 6 micrometers, wherein copolymer (F) is a partially fluorinated copolymer; 
 b) from 70 to 85% in weight/total weight of the solid portion consists of a second powder of at least one copolymer (F′) in the form of particles having average size (D50) from 20 to 90 micrometers, wherein copolymer (F′) is a partially fluorinated copolymer which is the same as or different from copolymer (F); 
 wherein the average particle size is measured according to test method ASTM D1921. 
 
     
     
       2. The composition according to  claim 1  wherein the particles of the first powder have an average size (D50) about 5 micrometers, and/or the particles of the second powder have an average size (D50) about 30 or about 80 micrometers. 
     
     
       3. The composition according to  claim 1 , wherein copolymer (F) and/or copolymer (F′) comprises:
 i. from 1 to 75 mol % of recurring units derived from at least one ethylenically unsaturated non-fluorinated monomer, which comprises at least one hydrogen atom; and 
 ii. from 25 to 99 mol % of recurring units derived from at least one fluorinated monomer. 
 
     
     
       4. The composition according to  claim 3 , wherein copolymer (F) and/or copolymer (F′) is a copolymer of tetrafluoroethylene and/or chlorotrifluoroethylene with ethylene, propylene and/or isobutylene, wherein the molar ratio of non-fluorinated monomer to the fluorinated monomer is from 70:30 to 30:70, and wherein said copolymer optionally contains 0.1 to 30 mol % of one or more fluorinated comonomer and/or of one or more non-fluorinated hydrogen-containing comonomer. 
     
     
       5. The composition according to  claim 4 , wherein copolymer (F) and/or copolymer (F′) is an ETFE- or ECTFE-based copolymer. 
     
     
       6. The composition according to  claim 4 , wherein copolymer (F) and/or copolymer (F′) contains 0.1 to 30 mol % of one or more fluorinated comonomers selected from the group consisting of 3,3,3-trifluoro-2-trifluoromethylpropene (HFIB), perfluoropropylvinylether (PPVE), 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole (TTD) and/or of one or more non-fluorinated hydrogen-containing comonomers selected from the group consisting of vinyl acetate, vinyl acrylatepropionate, vinyl-2-ethylhexanoate, ethyl acrylate, n-butyl acrylate, acrylic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, (hydroxy)ethylhexyl acrylate, and mixtures thereof. 
     
     
       7. The composition according to  claim 1 , wherein the weight of the solid portion is 20 to 50% in weight/total weight of the composition. 
     
     
       8. The composition according to  claim 1 , further comprising a water-miscible organic solvent in 0.1 to 20% weight/total weight of the composition. 
     
     
       9. The composition according to  claim 1 , wherein copolymer (F) and copolymer (F′) are the same partially fluorinated copolymer. 
     
     
       10. The composition according to  claim 1 , further comprising a rheology modifier. 
     
     
       11. A process for manufacturing the composition of  claim 1 , the process comprising blending in an aqueous solvent system a solid portion comprising a first powder of copolymer (F) particles having average size (D50) from 3 to 6 micrometers and a second powder of copolymer (F′) particles having average size (D50) from 20 to 90 micrometers, wherein the weight of the first powder is from 15 to 30% in weight with respect to the total weight of the solid portion and the weight of the second powder is from 85 to 70% in weight with respect to the total weight of the solid portion. 
     
     
       12. A coating comprising the composition of  claim 1 . 
     
     
       13. An article coated using the composition of  claim 1 . 
     
     
       14. The composition according to  claim 4 , wherein the molar ratio of non-fluorinated monomer to the fluorinated monomer is from 35:65 to 65:35. 
     
     
       15. The composition according to  claim 14 , wherein the molar ratio of non-fluorinated monomer to the fluorinated monomer is 50:50. 
     
     
       16. The composition according to  claim 5 , wherein copolymer (F) and/or copolymer (F′) is an ECTFE-based copolymer. 
     
     
       17. The composition according to  claim 6 , wherein the one or more non-fluorinated hydrogen-containing comonomers is selected from the group consisting of n-butyl acrylate, acrylic acid, and mixtures thereof.